The inventor, while working in the plumbing field has found the need for the purification of run-off water from residential and commercial properties. With the increased concerns of environmental controls placed on the run-off waters that are contaminating our streams, flood control channels, and estuaries eventually running into the oceans, there is a need for purification. Air borne contaminants landing on rooftops along with oils on driveways and parking lots comprise a major portion of these contaminants and need to be filtered before running off. It is easy to say that the public utilities should solve the problem, but a more logical solution is to solve it on a smaller scale at individual residential and commercial sites. Some up-scale housing developments are taking the lead and requiring that the run-off water from the roof pass through a filter system before being transferred into the flood control or sewer system. This is where the inventor initially worked out the unique integrated belowground vault with filter catch basin. This system allows the run-off water to enter into a belowground vault and pass through a commercially available replaceable filter before being transferred out to the flood control system or out through a French drain consisting of a cavity filled with drain gravel and positioned below the integrated belowground vault with filter catch basin. A layer of filter cloth can optionally be placed over the drain gravel. The depth of the French drain cavity is generally determined by the absorption rate of the subsoil, and in some cases may be the only way of removing the run-off water. The majority of the time run-off water comes in small amounts and can easily be filtered. However, in the event of heavy rainfall, a specially designed filter having an overflow opening may be used to divert excess water into the flood control system.